Lyndon Johnson had been president less than three months when confronted with a touchy international problem. Not surprisingly, it involved a familiar nemesis, Cuba. Hardly a year had passed since the Kennedy administration bargained the release of more than 1,000 prisoners locked up by Fidel Castro after our abortive Bay of Pigs invasion.

Once again, the prickly Castro seemed gleeful to be having a beef with Washington. It came about when the U.S. Coast Guard challenged the presence of four Cuban fishing boats that had ventured near the Florida coastline - clearly closer than allowed by international law.

Such intrusions are customarily resolved by a simple apology and/or a warning via official channels to the boat owners involved. Two complicating factors were in play in 1964, however. The government of Ecuador was regularly charging San Diego-based tuna boats with similar violation of its coastal waters. And Cuba's new young pro-communist ruler, then as now, was determined to show no servility toward a government he still detests.

Castro's response to our Coast Guard's action? He ordered water shut off to the U.S. Naval Base at Guantanamo, in southeastern Cuba. He knew he could get away with it. Under a treaty entered into long before its 1959 revolution, Cuba regularly had sold water to the U.S. base, which lacked a natural source of fresh water. Now, without warning or legal steps to cancel the Guantanamo lease, Cuba's new strongman took an action aimed to leave us high and dry.

American reaction was swift, and vindictive. Arizona's hawkish Sen. Barry Goldwater, already preparing to run against President Johnson in 1964, demanded that Johnson send a brigade of Marines to turn the water on again.

The Guantanamo base itself was commanded by a notably bellicose war hero, Rear Adm. John Bulkeley. He was the PT boat commander remembered for evacuating Gen. Douglas MacArthur from beleaguered Corregidor, in the Philippines. It was a source of quiet amusement among fellow officers that Bulkeley kept his ceremonial sword constantly sharpened.

But Bulkeley's most strident move came in response to Castro's complaint that the base was still siphoning water from his disputed pipeline. Bulkeley invited the press to watch engineers sever the line at the spot it entered the naval base.

But White House advisers warned Johnson to avoid reckless action against our tiny neighbor. They reminded him of the calm leadership President Kennedy had shown during the perilous Cuban missile crisis of October 1962. Instead of the armed assault many military leaders had then urged, Kennedy ordered a blockade of Havana harbor, and he decreed that incoming Soviet vessels would be halted and searched at sea. But no rough stuff.

Johnson briefly supplied Guantanamo's water needs by tanker. This could not long continue, however, without seeming to hand Castro a triumph he would eagerly exploit before the world. As things worked out, the president's political crisis was eventually eased not by Pentagon strategists, but by more wonkish minions at the Interior Department. They directed the president's attention to something of which the White House may have been only dimly aware. To wit, Interior's minuscule Office of Saline Water had been successfully desalting seawater for more than a year by processing it through a small demonstration plant it had built on Navy land near the tip of San Diego's Point Loma. This operation was gratuitously contributing some 50,000 gallons a day to San Diego's municipal water system.

But all this had been happening nearly 4,000 miles from where the cunning Castro was playing plumber in chief. Could a plant the size of Interior's "demonstration" be disconnected, picked up and shipped virtually intact to a new home in the Caribbean?

Johnson hardly waited for anyone's opinion on this. Piece by huge piece, the Point Loma contrivance was disassembled, each part tagged and loaded aboard freighters. In a matter of weeks, the "demonstration" plant was reassembled and producing - as it still does - a supply of fresh water to replace what we used to buy from Old What's-His-Face.

Desalt seawater? It's still more expensive than pumping our limited supply from the Colorado River. But Southern California - much of it virtually a desert - anticipates a possibly doubled population by mid-century. How shall we meet its water needs?

The huge company, Poseidon Resources, having won California's Coastal Commission approval for a commercial desalting operation alongside the coastal generating plant north of San Diego, awaits only an OK of proposed methods for mitigating the anticipated damage to marine life and the outcome of a lawsuit on that subject.

We should all be watching, even if Castro could not care less.

Van Deerlin represented a San Diego County district in Congress for 18 years.